The present invention provides a device intended for use in fracturing hardened material, such as rock, stone, concrete and the like, into small manageable units. More specifically, the present invention is intended for use in such industries as quarrying, mining, road construction and destruction and building construction and destruction. While the applications and uses of the present invention are unlimited in nature, the invention will be described herein with reference to use in the quarry and mining industry for the purpose of extracting blocks of quarry material such as granite, marble and the like. However, this description with regard to quarry and mining use are not intended to be limiting upon the scope of potential applications of the fracture device of this invention.
The estimated raw quarry production, world-wide, is approximately 40 million tons each year. The quarry material is most commonly removed from enormous quarries where large blocks of material are extracted, reduced in size, and shipped to stone cutters for further reduction in size. The most common method of extraction is provided by boring a line of holes, generally at six inch intervals, into the material formation or bedrock to create side cuts and an undercut to form a large block or cube of rock. After the holes are bored, they are most commonly filled with explosive and the explosive is detonated to cleave or split the cube along the lines formed by the bored holes. If the proper amount of explosive is used, the large block of material is successfully separated from its bed and is then shipped to the next stage of production. This use of explosives, while time honored, has proven to be quite unreliable and dangerous. Because of the difficulties in quantifying the condition of the rock below the surface, the amount of explosive necessary to cleave or separate the block of rock from its bed is most frequently based upon knowledgeable guess work. If, by chance, not enough explosives are used, the block will not separate from its bed causing need for a new round of explosives to be utilized and delaying production of the quarry in an undesirable manner. To avoid the problems resulting from a failure to remove the block from its bed, most quarryman err on the side of maximum explosive usage. As a result, the block will be separated from its bed but can, at the same time, be substantially damaged as a result of fractures and cracks created by the maximized explosion. If the block of stone is excessively cracked and fractured, it will in most cases, fail upon reduction to smaller units, thereby resulting in excessive scrap. Scrap production for certain types of materials being quarried can range as high as 80% to 90% of the material removed from the quarry, obviously an undesirable and costly outcome.
Alternative methods of quarry production include the use of wedges which are manually or mechanically driven into the drilled holes to apply pressure to the bedrock along the lines formed by the drilled holes. This has proven to be an effective but time consuming and costly method of quarry production resulting in the general acceptance by the industry of the use of explosives, even allowing for the resulting inconsistencies and wasteful amounts of scrap. However, recent world-wide preoccupation dealing with increased control over explosive materials and growing concern over the environmental hazards created by the use of explosive materials has forced the quarry industry to seek safer means to separate or cleave rock in its quarries. Further, such environmental concerns are underscored when viewed in the mining industry. If explosives must be utilized in enclosed areas, maintenance of the structural integrity of the mines is of a major concern, as well as the potential for unwanted conflagration within the mine as a result of the use of explosives. Thus, there is tremendous continued interest in developing safe and environmentally benign methods of quarry and mining production.
One solution to the dilemma has been proposed by Clifford (U.S. Pat. No. 1,630,470), providing a hydraulic cartridge composed of a flexible envelope confined at its opposed ends in a manner designed to resist longitudinal expansion. As the hydraulic pressure within the envelope is increased, the envelope is free to expand laterally or transversely within the bore hole to exert pressure therein. The cartridge taught by the Clifford reference never provided a satisfactory answer for the problems facing the quarry industry. There was a large degree of in exactitude about the ability of the cartridge to properly expand in the appropriate direction without failure. The elastomeric outer shell or expansible outer shell of Clifford was most commonly prone to rupture resulting in loss of hydraulic pressure during use. As a result, the apparatus disclosed and taught by Clifford in 1927 never became a commercially viable product for reliably fracturing and splitting stone in quarry operations. Quarry operators continue to search for alternative methods of stone splitting and stone breaking.
More recently, an international publication from the World Intellectual Property Organization, WO86-02404, by Derman, takes the disclosures of the prior Clifford reference and attempts to overcome the deficiencies of Clifford. Derman provides a fracturing member having displacable walls formed from elastomeric material, for example a thick walled rubber hose which is displacable in a direction transverse to the axis of the bore. The displaceable walls are connected with a device for preventing uncontrolled expansion in the longitudinal direction. The Derman reference attacks the problem of the elastomeric material having a tendency to creep through the clearance space located between the members of the fracturing unit and the surrounding wall of the bore. Derman presents a variety of combinations and end member features for solving the creeping problem of the elastomeric wall. Most of the end members of Derman are expansible in a direction toward the walls and culminate with a greater diameter than the elastomeric wall to prevent longitudinal creeping of the elastomeric material as the material is expanded against the wall of the bore. Derman further discloses a fracturing member having a metallic body with a longitudinal opening which contains an expansible rubber element. Rigid piston members are positioned in the longitudinal Opening and as fluid pressure is applied to the rubber element and the rubber expands, the pistons are displaced in a transverse direction. The pistons are described as being composed of a relatively rigid material, for example, nylon, while the walls of the body element are composed of metal. While the Derman reference provides substantially improved teachings over the Clifford reference, the embodiments taught by Derman have not proven effective in a commercial sense. The preferred structure of Derman, having an expansible outer layer with expansible end caps to eliminate longitudinal expansion of the expansible material between the fracture member and the wall of the bore, does not overcome the inherent deficiencies of having an expansible elastomeric member which comes into contact with the bore of the quarry material. The alternative embodiment of Derman, which provides for a hardened elastomeric piston member to transversely expand against the wall of the bore is known to be prone to failure due to sharp edges and corners around which the elastomeric material within the hardened fracture member must expand. Further problems have been encountered as a result of the tubular elastomeric member failing to provide sufficient force in the desired transverse direction.
Therefore, a need remains for a highly reliable device for use in quarry and mining operations which is environmentally safe and improves upon the reliability of prior art devices, thereby eliminating the need for use of explosives and other highly unpredictable and unreliable methods of quarrying. This objective is met by the present invention.
Further, a need remains for a highly reliable device for use in fracturing hardened material into small manageable units which is environmentally safe and improves upon the reliability of prior art devices. This objective is met by the present invention.